Drop dispenser

ABSTRACT

A liquid dispenser for dispensing drops including a housing, a liquid reservoir, a discharge opening through which liquid can be discharged from the liquid reservoir, and a drop formation surface surrounding the discharge opening, at which surface the liquid accumulates in order to be discharged from the drop formation surface as a drop. The drop formation surface has an outer limiting contour, the shape of which deviates from a circular shape. The dispenser is used to prevent contamination of the liquid to be dispensed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from German Application No. 10 2012 214 426.9, filed Aug. 14, 2012, the disclosure of which is hereby incorporated by reference in its entirety into this application.

FIELD OF THE INVENTION

The invention relates to a liquid dispenser for dispensing drops, including a housing, a liquid reservoir, a discharge opening through which the liquid from the liquid reservoir can be discharged, and a drop formation surface surrounding the discharge opening, where the liquid accumulates in order to be discharged as a drop from the drop formation surface.

BACKGROUND OF THE INVENTION

Such liquid dispensers formed as drop dispensers are known from the prior art, for example from DE 102010048085 A1 and DE 102008001313 B3.

The almost inevitable problem with such drop dispensers is that along with the discharge of a drop, the main drop, a remainder, the so-called remaining drop, remains on the drop formation surface, which remaining drop subsequently either dries at the drop formation surface or is drawn back into the drop dispenser. This remaining drop poses a risk since it can cause contamination both on the drop formation surface and in the liquid reservoir.

Therefore, intentions are to minimize the remaining drop as much as possible in terms of its volume, so as to keep the contamination low, in particular in the case of drying of a drop on the drop formation surface. A smaller remaining drop results in a more rapid drying of the same and thus in a reduced risk of contamination.

The post published document DE 102011083355 A1 already intends to solve said problem by proposing a geometry of the drop formation surface which partly fills the remaining drop and reduces the liquid volume of the remaining drop as a result.

The object of the invention is to provide an alternative or additional option for reducing the volume of the remaining drop.

According to the invention this object is achieved in that the drop formation surface includes an outer limiting contour, the shape of which deviates from a circular shape.

The drop dispenser according to the invention includes, in accordance with drop dispensers of such type, a housing, which accommodates the liquid reservoir and from which housing the liquid can be delivered to the drop formation surface through the discharge opening. Generally, different types of delivery mechanisms can be considered for that purpose. In particular, it is provided in drop dispensers of such type as well as according to the invention that the walls of the housing surrounding the liquid reservoir can be deformed, so that by direct force application to the housing, which functions as a squeeze bottle, the volume of the liquid reservoir may be reduced. However, generally also other mechanisms such as a piston pump, for example, are conceivable and covered by the invention.

The aforementioned drop formation surface of a drop dispenser of such type as well as according to the invention is the surface provided externally relative to the discharge opening, which surface is completely wetted during the discharge of liquid through the discharge opening and beyond which formation surface a wetting does not take place on the external side of the housing. It will be explained in the following by what the outer limiting contour of the drop formation face is defined.

According to the invention, said limiting contour is not circular with respect to a view direction in the direction of the discharge axis defined by the discharge opening.

It turned out that a shape deviating from the common circular shape of the limiting contour at a comparable dimension of the drop formation surface hardly affects the liquid amount of the main drop to be discharged, but that it significantly reduces the size of the remaining drop remaining on the drop formation surface after the discharge of the main drop.

As a result, by changing the shape of the drop formation surface, the problem of the remaining drop can significantly be reduced in a very simple constructional manner.

The size of the drop formation surface or of the area enclosed by the limiting contour depends on the size of the drops to be obtained. It is considered to be particularly advantageous when the area enclosed by the limiting contour, which area is formed by the drop formation surface together with the cross-sectional area of the discharge opening, has a size between 1 mm² and 5 mm², in particular a size between 1.5 mm² and 2.5 m². As a result, drops in the range between approximately 35 μl and 40 μl may be obtained.

The aforementioned limiting contour which limits the drop formation surface towards the exterior and which represents the line for the liquid contained in the drop dispenser up to which line the liquid accumulates beyond the discharge opening prior to being discharged as a main drop, can be defined in different ways and means.

It is particularly advantageous when the limiting contour is formed by a sharp edge, where the plane and only slightly curved drop formation surface merges into an adjacent, conical or cylindrical housing section. As to prevent that the liquid flows over said edge, said edge preferably has a curvature radius of less than 0.2 mm, in particular less than 0.1 mm, and in particular advantageously has an edge angle of at least 30°.

Another option for defining the limiting line, however advantageously provided together with such a sharp-edged limiting edge, stipulates that the drop formation surface up to the limiting line has a more hydrophilic surface characteristic compared to surrounding housing parts. In such a case, in the course of the drop formation, the liquid wets only the drop formation surface arranged within the limiting contour due to the comparatively hydrophobic design outside of the limiting contour. The different hydrophilicity can be obtained by means of surfaces of the external faces of the dispensers which surfaces have preferably been manufactured from synthetic material. Also the structure of the dispenser or the structure of its discharge head being composed of a plurality of parts made of different synthetic material can cause the desired discontinuity in the hydrophilicity.

Preferably, the shape of the drop formation surface deviates significantly from the circular shape. That means that at least by the factor 1.2, preferably at least by the factor 1.5, the limiting contour is partly more distant from the discharge axis defined by the discharge opening than from a part of the limiting contour having a minimum distance to the discharge axis.

Furthermore, the area enclosed by the limiting contour is preferably at least 10% smaller than the inside area of a circle having a diameter corresponding to the maximum extension of the area enclosed by the limiting contour. Preferably, said area is even by at least 15% smaller than a corresponding circular area, particularly preferable by at least 20%.

With respect to the shape of the drop formation surface, very diverse designs are conceivable, which are advantageous as compared to the thus far common circular drop formation surface. A particularly simple shape is that where all partial sections of the limiting contour are configured either straight or curved with outward convexity. Thus, the limiting contour as a whole is formed curved with outward convexity. In the simplest case, that is achieved by a quadratic or triangular shape of the drop formation surface. The corners of such a square shape or triangle shape may preferably be rounded-off. Also an oval shape of the drop formation surface belongs to said category of shapes of the drop formation surface.

A design is particularly advantageous where at least partial sections of the limiting contour form notches that are curved with inward concavity and thus curved towards the discharge opening. It turned out that a shape of the drop formation surface where the limiting contour at least sectionally is curved inwards and thus towards the discharge axis, results in a particularly small remaining drop.

Even though already a single notch causes such an effect to a measurable extent, it is advantageous if a plurality of notches, preferably between two and six notches, in particular six notches, is provided.

The notches are preferably distributed uniformly over the circumference.

In the simplest embodiment, the drop formation surface is plane. Generally, concave or convex designs are appropriate as well. In particular a convex design with a drop formation surface slightly curved outwards is suitable to further reduce the volume of the remaining drop. Here, the curvature of the drop formation surface is designed such that a normal vector always includes an angle <15° with the discharge axis of the discharge opening.

Particularly preferred is the use of a drop formation surface of the described type in the case of drop dispensers having an outlet valve preventing the return flow of the liquid into the liquid reservoir. Particularly in the case of dispensers having such an outlet valve, the contamination of the remaining drop remaining at the external face is particularly disadvantageous.

The dispenser according to the invention is in particular provided for pharmaceutical liquids, in particular for ophthalmic liquids, and thus filled therewith in the delivery state. In particular, these are pharmaceutical liquids for treatment of increased intraocular pressure (glaucoma treatment), for treatment of dry eyes and for treatment of allergies and inflammations. In this case, these are in particular the molecule groups alpha-2-agonists, e.g. brimonidine, prostaglandin analogues (tafluprost, latanoprost, bimatoprost, travoprost), beta blockers, e.g. timolol, and carbonic anhydrase inhibitors, e.g. dorzolamide or hyaluronic acid based compounds, film formers, e.g. methylcellulose compounds and cyclosporine or antihistamines, e.g. olopatadine and levocabastine, steroids, e.g. loteprednol and dexamethasone, as well as non-steroidal anti-inflammatory drugs (NSAID), e.g. ketorolac.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects and advantages of the invention arise but from the claims also from the following description of a preferred exemplary embodiment of the invention, which is explained in in the following with reference to the drawings, in which:

FIG. 1 shows a drop dispenser according to the invention in an overall illustration,

FIGS. 2 and 3 show the discharge head of the dispenser according to FIG. 1 in a partially sectional side view and in a plan view, and

FIGS. 4 a to 4 f show a drop formation surface of the dispenser of the FIGS. 1 to 3 as well as five alternative shapes of such a drop formation surface.

DETAILED DESCRIPTION

FIG. 1 shows a drop dispenser 10 according to the invention in an overall illustration. Said drop dispenser 10 comprises a housing, which is formed by a bottle body 12, which represents the external wall of a liquid reservoir, and a discharge head 14.

At the distal end of the discharge head 14, a discharge opening 20 is provided which is surrounded by a drop formation surface 30.

The use according to the invention of the dispenser 10 of FIG. 1 provides that said dispenser, in a position with the discharge opening 20 facing downwards, is pressed together by force application to the bottle body 12 in the type of a squeeze bottle, wherein the volume reduction in the liquid reservoir results in liquid being fed through the discharge opening 20 and accumulating at the drop formation surface 30. Upon progressing volume reduction of the bottle body 12 during the actuation, the liquid continues accumulating at the drop formation surface 30 until it disengages for the most part from the drop formation surface 30 in the form of a main drop. A remaining drop remains at the drop formation surface 30.

Due to a spring-loaded outlet valve 18 illustrated in FIG. 2 in a highly schematic manner, the remained liquid amount of the remaining drop cannot return into the liquid reservoir. Instead, it remains externally at the drop formation surface 30 and dries there.

The drop formation surface has a shape that accelerates said drying process by causing that the volume of the remaining drop remains comparatively small after detachment of the main drop. The shape of the drop formation surface can be seen in FIG. 3 and in particular also in FIG. 4 a. Said drop formation surface 30 is limited outwards by means of a limiting contour 32, which forms a sharp edge to the adjacent, conical housing external faces 14 a. In the case of the dispenser of FIGS. 1 to 3 and 4 a, said limiting contour 32 is provided with a total of six notches 32 a and thus has almost the shape of a six-pointed star or of a six-leafed flower. Compared to a circular drop formation surface of the same size, the drop formation of the main drop is hardly influenced by said geometry.

Tests revealed that the reduction of the drop volume compared to a circular drop formation surface of the same size is less than 10%. That may be compensated by a slightly larger area of the drop formation surface 30, where required. However, the tests have also shown that the volume of the remaining drop after discharge of a drop is drastically reduced. The remaining drop remaining at the drop formation surface 30 according to the dispenser of the FIGS. 1 to 3 and 4 a, is not more than approximately half the size of the remaining drop that would remain at a circular drop formation surface having an equal area.

As a result, the problem of the remaining drop is significantly reduced by simple ways and means. In practice, the dispenser of FIGS. 1 to 3 is capable of producing main drops of a volume of more than 40 μl, while the remaining drop has a volume of less than 4 μl. That is a very good volume ratio.

FIGS. 4 b to 4 f show alternative shapes of a drop formation surface 30. Said drop formation surfaces correspond to the drop formation surface of FIG. 4 a in that likewise the maximum spaced apart parts of the limiting contour are significantly more distant from a discharge axis 2 than the parts having the minimum distance thereto.

In the case of the embodiments according to FIGS. 4 b, 4 c and 4 f, oval, triangular and quadratic base shapes were used. Along their respective edges, also the quadratic and the triangular shape are convexly curved, that not being mandatory. The embodiment according to FIG. 4 e provides a star-shaped shape with 4 rays facing away from the discharge opening 20, between which rays correspondingly shaped notches 32 a are provided. In the case of FIG. 4 c, the drop formation surface 30 comprises notches merely at two opposing sides.

The above-mentioned shapes of FIGS. 4 b to 4 f all result in a significant volume reduction of the remaining drop. In the case of a respective dimensioning of the drop formation surfaces of the FIGS. 4 b to 4 f such that the main drop formed thereby is the size of that with a circular drop formation surface, the volume of the remaining drop is reduced by between approximately 20% (drop formation surfaces of FIGS. 4 b, 4 c and 4 f) and up to 50% (drop formation surfaces of FIG. 4 a).

It applies to all drop formation surfaces 30 of FIGS. 4 a to 4 f that said surfaces may be limited by means of a sharp edge, as illustrated in FIGS. 1 to 3, and/or by means of a discontinuity in the hydrophilicity of the surfaces inside and outside of the limiting contours 32. 

1. A liquid dispenser for dispensing drops comprising a housing, a liquid reservoir, a discharge opening through which liquid from the liquid reservoir can be discharged, and a drop formation surface surrounding the discharge opening, where the liquid accumulates in order to be discharged as a drop from the drop formation surface, wherein the drop formation surface has an outer limiting contour, the shape of which deviates from a circular shape.
 2. The liquid dispenser according to claim 1, wherein the limiting contour of the drop formation surface is formed by a limiting edge having a curvature radius of less than 0.1 mm.
 3. The liquid dispenser according to claim 1, wherein the limiting contour of the drop formation surface is formed in that within the limiting contour, the drop formation surface is formed more hydrophilic than the surrounding external faces of the housing outside of the limiting contour.
 4. The liquid dispenser according to claim 1, wherein the part of the limiting contour at maximum distance to a discharge axis defined by the discharge opening is more distant from the discharge axis at least by a factor 1.2 than the part of the limiting contour at minimum distance.
 5. The liquid dispenser according to claim 1, wherein all partial sections of the limiting contour are formed either straight or curved with outward convexity.
 6. The liquid dispenser according to claim 1, wherein at least partial sections of the limiting contour form notches, which are curved with inward concavity.
 7. The liquid dispenser according to claim 6, wherein a plurality of notches is provided.
 8. The liquid dispenser according to claim 7, wherein the plurality of notches are distributed uniformly over the circumference of the drop formation surface and/or at least three notches are provided.
 9. The liquid dispenser according to claim 1, wherein the drop formation surface is formed concavely or convexly. 